Method for connection reconfiguration in cellular radio network

ABSTRACT

The invention relates to a method for reconfiguring a cellular radio network connection comprising a network part having a connection to a mobile station through at least one radio bearer. According to the invention, a first party of the connection, i.e. the network part or the mobile station, sends a second party of the connection, i.e. the mobile station or the network part, a reconfiguration request message concerning at least one radio bearer. The second party of the connection possibly replies to this by sending the first party of the connection a reply message to the radio bearer reconfiguration request message. The radio bearer reconfiguration request message comprises at least one radio bearer identifier and, for example, bearer quality of service of the radio bearer in question. The possible reply message comprises at least one radio bearer identifier and possibly also bearer quality of service assigned to the radio bearer in question, or a cause for a failed reconfiguration of the radio bearer in question.

This is a divisional application of U.S. Ser. No. 09/627,526, filed Jul.28, 2000. The disclosure of the prior application is hereby incorporatedby reference.

FIELD OF THE INVENTION

The invention relates to a method for reconfiguring a cellular radionetwork connection. The reconfiguration particularly concerns a radiobearer providing a connection between a network part and a mobilestation.

BACKGROUND OF THE INVENTION

In the GSM system connection reconfiguration concerns the modifying of acall mode. The procedure is known as in-call modification. The term‘mode’ means the operational status of a call; it can be for instance astandard speech mode, data mode, fax mode, an alternating speech/datamode or an alternating speech/fax mode. When a connection isreconfigured, its mode can thus be changed e.g. from a speech mode to adata mode. In case the channel used for the connection does not supportthe required characteristics, channel configuration can be changed. Thesolution known from the GSM system is not, however, applicable for usein UMTS (Universal Mobile Telephone System) described below. The reasonfor this is that in the UMTS a single connection can simultaneously useone or more radio bearers. The characteristics of the radio bearers mayhave to be modified upon establishment of or during a connection.

The term ‘radio bearer’ refers to a service provided by a network layer.Multimedia service typically uses a plural number of radio bearerssimultaneously for providing a service. Video telephony, for example,may require four different radio bearers: transmission of speech andimage both use separate radio bearers for uplink and downlink. Amultimedia service, such as video telephony, can also be implemented byusing only one radio bearer per transmission direction, thereby avoidingthe problem of synchronization between radio bearers of the sametransmission direction. Radio bearer parameters comprise most of thefirst and second layer operational parameters. A radio bearer user,however, does not know the parameters of lower layers. Therefore theradio bearer user is not aware of how the radio bearer provides itsservices, i.e. whether it uses a half of a TDMA time slot, one time slotor a plural number of them, or one or more CDMA spreading codes.

A radio bearer is defined by a set of parameters or attributes thatconcern the traffic or quality characteristics of a service provided. Aradio bearer is not to be considered similar to a logical channel, whichis a service provided by a data link layer.

BRIEF DESCRIPTION OF THE INVENTION

An object of the invention is therefore to provide a method and anequipment implementing the method in such a way that the above problemscan be solved. This is achieved with the method described below, whichis a method for reconfiguring a cellular radio network connectioncomprising a network part, the network part having a connection to amobile station through at least one radio bearer. According to themethod, a first party of the connection sends to a second party of theconnection a radio bearer reconfiguration request message involving atleast one radio bearer; the second party of the connection sends to thefirst party of the connection a reply message to the radio bearerreconfiguration request message.

The invention also relates to a cellular radio network comprising: aprotocol software of a network layer of a network part, the softwarebeing arranged to have a connection to a mobile station through at leastone radio bearer; a protocol software of a network layer of the mobilestation, the software being arranged to have a connection to the networkpart through at least one radio bearer. The protocol software of thenetwork layer of the network part is arranged to transmit to theprotocol software of the network layer of the mobile station a radiobearer reconfiguration request message involving at least one radiobearer; the protocol software of the network layer of the mobile stationis arranged to transmit to the protocol software of the network layer ofthe network part a reply message to the radio bearer reconfigurationrequest message.

The invention further relates to a cellular radio network comprising: aprotocol software of a network layer of a network part, the softwarebeing arranged to have a connection to a mobile station through at leastone radio bearer; a protocol software of a network layer of the mobilestation, the software being arranged to have a connection to the networkpart by means of at least one radio bearer. The protocol software of thenetwork layer of the mobile station is arranged to transmit to theprotocol software of the network layer of the network part a radiobearer reconfiguration request message involving at least one radiobearer; the protocol software of the network layer of the network partis arranged to transmit to the protocol software of the network layer ofthe mobile station a reply message to the radio bearer reconfigurationrequest message.

The invention further relates to a method for reconfiguring a cellularradio network connection comprising a network part, the network parthaving a connection to a mobile station through at least one radiobearer. A first party of a connection transmits to a second party of theconnection a radio bearer reconfiguration request message involving atleast one radio bearer.

The preferred embodiments of the invention are disclosed in thedependent claims.

The invention is based on that either of the communicating parties canrequest, when needed, a radio bearer reconfiguration.

A method and system of the invention provide several advantages. Thesolution enables reconfiguration to be flexibly implemented in a systememploying radio bearers. A plural number of radio bearers can besimultaneously reconfigured, the number of messages needed being therebyreduced, which in turn decreases the load on radio resources. Whennecessary, reconfiguration of radio bearers used for signalling can becarried out at connection set-up, thus avoiding a reallocation ofsignalling radio bearers that would perhaps otherwise be needed.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail inconnection with preferred embodiments and with reference to the attacheddrawings, in which

FIG. 1 illustrates an example of a cellular radio network structure;

FIG. 2 illustrates a transceiver structure;

FIG. 3 illustrates cellular radio network protocol stacks;

FIG. 4A is a message sequence diagram illustrating a reconfigurationprocedure of the invention initiated by a mobile station;

FIG. 4B is a message sequence diagram illustrating a reconfigurationprocedure of the invention initiated by a network part;

FIG. 5 illustrates protocol stacks of an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, a typical cellular radio network structure ofthe invention will be described. FIG. 1 only comprises the blocks thatare essential for the description of the invention, although it isapparent to a person skilled in the art that a common cellular radionetwork also comprises other functions and structures which need not bediscussed in greater detail here. The examples describe a cellular radionetwork employing TDMA (Time Division Multiple Access), the inventionnot being, however, restricted to it. The invention can be applied toGSM-based cellular radio networks, in other words, to systems that areat least partially based on GSM specifications. One example is the UMTS(Universal Mobile Telephone System).

A cellular radio network typically comprises a fixed networkinfrastructure, i.e. a network part 128, and mobile stations 150, whichmay be fixedly mounted, vehicle mounted or hand-held portable terminals.The network part 128 comprises base stations 100. A plural number ofbase stations 100 are, in turn, controlled in a centralized manner by abase station controller 102 communicating with them. A base station 100comprises transceivers 114. A base station 100 typically comprises 1-16transceivers 114. In TDMA radio systems, for example, a transceiver 114offers radio capacity to one TDMA frame, i.e. typically to eight timeslots.

The base station 100 comprises a control unit 118 which controls theoperation of the transceivers 114 and a multiplexer 116. The multiplexer116 arranges traffic and control channels used by a plural number oftransceivers 114 on a single data link 160.

The transceivers 114 of the base station 100 have a connection to anantenna unit 112 which is used for providing a bi-directional radioconnection 170 to a mobile station 150. The structure of the framestransmitted in the bi-directional radio connection 170 is alsodetermined in detail and the connection is referred to as an airinterface.

FIG. 2 illustrates in greater detail the structure of a transceiver 114.A receiver 200 comprises a filter blocking frequencies outside a desiredfrequency band. A signal is then converted to an intermediate frequencyor directly to baseband, and in this form the signal is sampled andquantized in an analog-to-digital converter 202. An equalizer 204compensates for interference caused for instance by multi-pathpropagation. From the equalized signal, a demodulator 206 takes a bitstream, which is transmitted to a demultiplexer 208. The demultiplexer208 separates the bit stream from the separate time slots into itslogical channels. A channel codec 216 decodes the bit stream of theseparate logical channels, i.e. decides whether the bit stream issignalling data, which is transmitted to a control unit 214, or whetherthe bit stream is speech, which is transmitted 240 to a speech codec 122of the base station controller 102. The channel codec 216 also performserror correction. The control unit 214 performs internal controlfunctions by controlling different units. A burst former 228 adds atraining sequence and a tail to the data arriving from the speech codec216. A multiplexer 226 assigns a specific time slot to each burst. Amodulator 224 modulates digital signals to a radio frequency carrier.This operation has an analog nature, therefore a digital-to-analogconverter 222 is needed for performing it. A transmitter 220 comprises afilter restricting the bandwidth. In addition, the transmitter 220controls the output power of a transmission. A synthesizer 212 arrangesthe necessary frequencies for the different units. The synthesizer 212comprises a clock which may be locally controlled or it can be centrallycontrolled from somewhere else, for instance from the base stationcontroller 102. The synthesizer 212 creates the necessary frequencies bymeans of a voltage controlled oscillator, for example.

As shown in FIG. 2, the structure of the transceiver can be furtherdivided into radio frequency parts 230 and a digital signal processorincluding software 232. The radio frequency parts 230 comprise thereceiver 200, the transmitter 220 and the synthesizer 212. The digitalsignal processor including software 232 comprises equalizer 204,demodulator 206, demultiplexer 208, channel codec 216, control unit 214,burst former 228, multiplexer 226 and modulator 224. Theanalog-to-digital converter 202 is needed for converting an analog radiosignal to a digital signal and, correspondingly, the digital-to-analogconverter 222 is needed for converting a digital signal to an analogsignal.

The base station controller 102 comprises a group switching field 120and a control unit 124. The group switching field 120 is used forswitching speech and data and for connecting signalling circuits. Thebase station 100 and the base station controller 102 form a Base StationSystem 126 which additionally comprises a transcoder 122. The transcoder122 is usually located as close to a mobile switching centre 132 aspossible because this allows speech to be transmitted between thetranscoder 122 and the base station controller 102 in a cellular radionetwork form, which saves transmission capacity. In the UTMS the basestation controller 102 can be referred to as an RNC (Radio NetworkController).

The transcoder 122 converts different digital speech coding modes usedbetween a public switched telephone network and a cellular radionetwork, to make them compatible, for instance from the 64 kbit/s fixednetwork form to another form (such as 13 kbit/s) of the cellular radionetwork, and vice versa. The control unit 124 carries out call control,mobility management, collection of statistical data and signalling.

The UMTS uses an IWU 190 (Interworking Unit) to make the base stationsystem 126 interwork with a second generation GSM mobile switchingcentre 132 or a second generation packet transmission network supportnode 180. The IWU is not needed when the base station system isconnected to an UMTS mobile switching centre or to an UMTS support node.As shown in FIG. 1, a circuit-switched connection can be establishedfrom the mobile station 150 via the mobile switching centre 132 to atelephone 136 connected to a PSTN (Public Switched Telephone Network)134. A packet-switched connection, such as GSM phase 2+ packettransmission, i.e. GPRS (General Packet Radio Service), can also be usedin a cellular radio network. The connection between a packet network 182and the IWU 190 is created by a support node 180 (SGSN=Serving GPRSSupport Node). The function of the support node 180 is to transferpackets between the base station system and a gateway node (GGSN=GatewayGPRS Support Node) 184 and to keep record of the mobile station's 150location within its area.

The IWU 190 can be a physically separate device, as in FIG. 1, or it canbe integrated as part of the base station controller 102 or the mobileswitching centre 132. As FIG. 1 shows, when transcoding of the data tobe transferred is not allowed, packet transmission data is notnecessarily transferred through the transcoder 122 between the IWU 190and the group switching field 120.

The gateway node 184 connects the packet network 182 and a public packetnetwork 186. The interface can be provided by an Internet protocol or anX.25 protocol. The gateway node 184 encapsulates the internal structureof the packet network 182, thus masking it from the public packetnetwork 186, so for the public packet network 186 the packet network 182looks like a sub-network, and the public packet network can addresspackets to a mobile station 150 located in the sub-network and receivepackets from it.

A typical packet network 182 is a private network applying an Internetprotocol and conveying signalling and tunnelled user data. The structureof the network 182 can vary according to operator, both as regards itsarchitecture and its protocols below the Internet protocol layer.

The public packet network 186 can be for instance a global Internetnetwork into which a terminal 188, for instance a server, with aconnection to the network wants to transmit packets addressed to themobile station 150.

The mobile switching centre 132 is connected to an OMC (Operations andMaintenance Centre) controlling and monitoring the operation of a radiotelephone system. The OMC 132 is usually a fairly efficient computerprovided with a specific software. The control can also involve separateparts of the system, because control channels needed for control datatransfer can be arranged on data transmission connections establishedbetween different parts of the system.

Further, the personnel installing a network and controlling theoperations possibly have a portable computer including an EM (ElementManager) 140 at their disposal for the management of separate networkelements. The Figure shows an example in which the device 140 isconnected to a data transmission port located in the control unit 118 ofthe base station 100, thus enabling the operation of the base station100 to be monitored and controlled, for instance by examining andchanging the values of parameters regulating the operation of the basestation.

The structure of the mobile station 150 can be described utilizing thedescription of the transceiver 114 in FIG. 2. The structural parts ofthe mobile station 150 are operationally the same as those of thetransceiver 114. The mobile station 150 additionally comprises: a duplexfilter between the antenna 112 and the receiver 200 and between theantenna 112 the transmitter 220, interface parts and a speech codec. Thespeech codec is connected to a channel codec 216 via a bus 240.

Since the present invention relates to the processing of protocols usedin a cellular radio network, an example illustrating the implementationof the necessary protocol stacks will be described with reference toFIG. 3. The left-most protocol stack in FIG. 3 is a protocol stacklocated at the mobile station 150. The next protocol stack is in thebase station system 126. A third protocol stack is located in the IWU190. The right-most protocol stack is located in the mobile switchingcentre 132. The air interface 170 provided by means of the radioconnection 170 between the mobile station 150 and the base stationsystem can also be referred to as an Um interface. An interface 162between the base station system 126 and the mobile switching centre 132is called an A interface. The interface between the base station system126 and the IWU is an lu interface 300.

The protocol stacks are formed according to an OSI (Open SystemsInterconnection) model of the ISO (International StandardizationOrganization). In the OSI model protocol stacks are divided into layers.There can be seven layers. A layer in each device 150, 126, 190, 132communicates logically with a layer in another device. Only the lowest,physical layers communicate with each other directly. Other layersalways use services provided by the layer below. A message musttherefore physically travel in a vertical direction between the layers,and only in the lowest layer the message travels horizontally betweenthe layers.

The actual bit level data transmission takes place through the lowest(the first) layer, i.e. a physical layer Layer 1. In the physical layerare determined mechanical, electronic and operational characteristicsfor connecting to a physical transmission link. The physical layer inthe air interface 170 of the GSM is provided by means of TDMAtechnology. In the UMTS the physical layer is provided by using WCDMAand TD/CDMA. The physical layer provides a second layer with transportservices on transport channels. The transport channels are RACH (RandomAccess Channel), FACH (Forward Access Channel), PCH (Paging Channel),BCH (Broadcast Channel) and DCH (Dedicated Channel). Transport channelsdetermine the method and the parameters for transferring data in thephysical layer. Transport channel parameters include: encoding, i.e.outer and inner coding, interleaving, bit rate and mapping to physicalchannels. In WCDMA the physical channel used by the transport channelsis determined by codes. A channelization code, i.e. spreading code,determines the spreading ratio, thus determining also the maximum bitrate to be used. The channelization code is separately determined foruplink and downlink and, depending on the bit rate needed, one or moreparallel codes can be simultaneously used. A scrambling code, in turn,separates different mobile stations from one another on uplink anddifferent cells or sectors of cells on downlink.

The next (the second) layer, i.e. a data link layer, uses the servicesof the physical layer to provide reliable data transmission, whichincludes correction of transmission errors, for example. The data linkprovides upper layers with data transmission services on logicalchannels. The logical channels comprise CCCH (Common Control Channel),PCCH (Paging Control Channel), BCCH (Broadcast Control Channel), DCCH(Dedicated Control Channel) and DTCH (Dedicated Traffic Channel). Thelogical channels determine the data to be transmitted, unlike transportchannels, which determine the method and the parameters to be used fortransferring data. The DTCH provides services to upper layers of a userplane, all the other logical channels to upper protocol layers of acontrol plane.

The data link layer at the air interface 170 is divided into an RLC/MACsublayer and an LLC sublayer. In the RLC/MAC sublayer, the RLC part isresponsible for segmenting and collecting the data to be transmitted. Inaddition, the RLC part masks quality fluctuations in the radio interface170 of the physical layer from the upper layers. A sublayer RRC, to bedescribed later, controls the allocation, reconfiguration and releasingof physical code channels and the transport channels provided by thephysical layer. The MAC part carries out the actualallocation/configuration/releasing by command of the RRC sublayer. TheMAC part can also indicate to the RRC sublayer that allocation isneeded. On the user plane the LLC sublayer controls the data flow at theinterface between the second and the third layer. The LLC transfers thereceived data flow on the radio connection 170 through error detectionand correction levels required by the quality of service of the offeredservice. On the control plane, a radio network sublayer described belowcommunicates directly with the RLC/MAC sublayer.

The third layer, i.e. the network layer, offers to the upper levelindependence of data transmission and switching techniques taking careof the connection between mobile stations. The network layer carries outconnection set-up, maintenance and releasing, for example. A GSM networklayer is also known as a signalling layer. It has two main functions: toroute messages and to provide for the possibility of a plural number ofindependent, simultaneous connections between two entities.

The network layer of a common GSM system comprises a connectionmanagement sublayer CM, a mobility management sublayer MM and a radioresource management sublayer.

The radio resource management sublayer is responsible for frequencyspectrum management and for the reactions of the system to changingradio circumstances. It is further responsible for maintaining ahigh-quality channel, e.g. by taking care of channel selection, thereleasing of a channel, possible frequency hopping sequences, poweradjustment, timing, reception of mobile station measurement reports,adjustment of a timing advance, ciphering settings, handover betweencells. Messages of this sublayer are transferred between the mobilestation 150 and the base station controller 102.

The mobility management sublayer MM handles such consequences caused bythe mobility of a mobile station user which do not directly relate tothe operation of the radio resource management sublayer. In a fixednetwork this sublayer would take care of checking user authorities andconnecting the user to the network. In cellular radio networks thesublayer in question thus supports user mobility, registration andmanagement of data caused by mobility. The sublayer also checks mobilestation identity and the identities of the services allowed. Datatransmission concerning the sublayer takes place between the mobilestation 150 and the mobile switching centre 132.

The connection management sublayer CM manages all operations associatedwith circuit-switched call management. The operations involved areprovided by a call management entity. In addition, other services, suchas SMS (Short Message Service), are provided by separate entities. Theconnection management sublayer does not detect user mobility. The GSMconnection management sublayer operations are therefore almost directlyinherited from the ISDN (Integrated Services Digital Network) of thefixed network. The call management entity sets up, maintains andreleases calls. It has specific procedures which it applies to callsoriginated by and terminating to the mobile station 150. Also in thissublayer messages are transferred between the mobile station 150 and themobile switching centre 132.

The TDMA technique employed in an ordinary physical GSM layer isreplaced in the UMTS by a broadband CDMA technique (Code DivisionMultiple Access) when different frequency bands are used for uplink andfor downlink and by a broadband combination of CDMA and TDMA techniqueswhen one and the same frequency band based on a time division duplexmethod is used for both uplink and downlink. In this case the GSM radioresources management sublayer can not be re-used in the UMTS, but it isreplaced by a radio network sublayer RNL providing correspondingservices upward. The radio network sublayer can be divided into RBC(Radio Bearer Control) and RRC (Radio Resource Control) sublayers, butit can also be kept as a single entity. When kept as a single entity, itcan also be called an RRC sublayer. If the division into sublayers isapplied, then the RRC sublayer performs e.g. broadcasting and paging ofcell data, processing of mobile station 150 measurement results, andhandovers. The RBC sublayer provides the logic connection establishment,thereby determining e.g. radio bearer bit rate, bit/error ratio andwhether the transmission concerned is packet-switched orcircuit-switched.

When upper protocol layers of second generation systems are used assuch, the mobile station 150 needs a UAL (UMTS Adaptation Layer)sublayer between the mobility management and radio network sublayers,the UAL sublayer changing the primitives of a upper mobility managementsublayer to primitives of a lower radio network sublayer. The UAL layerenables a plural number of separate mobility management sublayers (suchas GPRS and GSM mobility management sublayers) to be arranged into oneand the same radio network sublayer.

The only network sublayers processed in the base station system 126 arethe radio network sublayer; messages of the connection management andmobility management sublayers are transparently processed, in otherwords, they are simply transferred back and forth through specificsublayers. A RANAP sublayer (Radio Access Network Application Part)provides procedures for negotiating and managing both circuit-switchedand packet-switched connections. It corresponds to BSSAP (Base StationSystem Application Part) in the GSM, BSSAP comprising BSSMAP (BaseStation System Management Part) and DTAP (Direct Transfer ApplicationPart).

Lower layers of the lu interface 300 can be implemented for instance bymeans of ATM (Asynchronous Transfer Mode) protocols: SAAL/SS7(Signalling ATM Adaptation Layer/Signalling System Number 7), AAL (ATMAdaptation Layer).

The IWU 190 comprises RANAP, SAAL/SS7, AAL sublayers and physical layerscorresponding to those of the base station system 126.

The IWU 190 and the mobile switching centre 132 further comprise aBSSMAP sublayer through which data associated with a particular mobilestation 150 and control data associated with the base station system 126are transferred between the IWU 190 and the mobile switching centre 132.

In the A interface the first and the second sublayer are implemented bymeans of MTP and SCCP sublayers (Message Transfer Part, SignallingConnection Control Part). Their structure is simpler than in the airinterface 170, because mobility management, for example, is not needed.

As we have now described, with reference to FIGS. 1, 2 and 3, an exampleof a system and system protocols where the invention can be used, we canproceed to describe the actual method of the invention. The aboveprotocol description showed that the operation according to theinvention takes place in the radio network sublayer RNL in particular,and specifically in its RBC sublayer, if the sublayer division inquestion is applied.

If the division into sublayers is not applied, then there is no RBCsublayer and therefore the radio network sublayer RNL can be termed anRRC sublayer, according to its only sublayer; protocol stacks of apreferred embodiment based on this are illustrated in FIG. 5. Since theinvention mainly concerns the control plane, FIG. 5 only shows controlplane protocol stacks. The main parts of a mobile phone system are acore network, a UMTS terrestrial radio access network UTRAN and a mobilestation MS. The mobile station can also be referred to as a UE (UserEquipment). The interface between the core network and UTRAN is calledlu and the air interface between UTRAN and a mobile station is calledUu.

UTRAN comprises radio network subsystems. A radio network subsystemcomprises a radio network controller and one or more so-called B nodes,i.e. base stations, so it is approximately similar to a GSM base stationsystem.

The core network comprises a mobile phone system infrastructure outsideUTRAN, such as a mobile switching centre.

FIG. 5 illustrates protocol stacks used by the mobile station MS, theradio access network UTRAN and the mobile switching centre MSC. Unlikein FIG. 3, the IWU is not shown because it is assumed that the mobileswitching centre MSC employed is designed for the UMTS. The physicallayer in the air interface Uu is implemented by means of a broadbandCDMA technique WCDMA LI. The RLC and MAC sublayers follow next. The LLCsublayer is not used on the control plane, the RRC sublayer beingdirectly connected to the RLC/MAC sublayer. Lower transport layersTRANSPORT LAYERS of the lu interface are not illustrated in such detailas in FIG. 3, because they can be implemented in various ways. Otherwisethe description of FIG. 3 also applies, to the extent appropriate, toFIG. 5.

FIG. 4A is a message sequence diagram illustrating how the mobilestation radio network sublayer MS RNL communicates with the network partradio network sublayer NP RNL when performing radio bearerreconfiguration. FIG. 4A does not show all details of the communication,i.e. how messages travel in lower data link layers and physical layers.The communication illustrated is known as a peer-to-peer communication.The reconfiguration request message is a radio network sublayer message.

Radio bearer reconfiguration can be initiated by

-   -   1. an upper layer, after service parameters are negotiated on a        call control plane;    -   2. the RRC sublayer, by applying algorithms guiding the use of        radio resources;    -   3. even a lower level, such as a MAC sublayer, because of its        traffic volume monitoring, or a physical layer, after it has        reached the maximum transmission power limit.

The reason for reconfiguration may be an overload situation ordegradation of the radio bearer quality, for example. Radio bearerreconfiguration can be requested both by the sender and the receiver:the sender when needing for instance additional capacity, and thereceiver when detecting that the quality is too low.

In FIG. 4A the mobile station radio network sublayer MS RNL sends 400A areconfiguration request message BEARER_RECONF_REQ to the network partradio network sublayer. The message comprises a radio Bearer IdentifierBID and Quality of Service BEARER QOS of the bearer in question. Themessage may comprise more than one BID/BEARER QOS pair, i.e. one messagecan be used for requesting the reconfiguration of a plural number ofseparate radio bearers.

The requested reconfiguration 402A is carried out in the network part.If the reconfiguration is successful, the network part sends 404A areply message BEARER_COMPL informing that the reconfiguration succeeded.The reply message comprises the radio bearer identifier BID and thequality of service BEARER QOS provided. Depending on the implementation,parameters of the LLC sublayer and/or the RLC sublayer can also betransferred. Another option is that the mobile station decodes from thequality of service parameter BEARER QOS the LLC sublayer and/or RLCsublayer parameters concerned, in which case they need not betransferred in the reply message BEARER_COMPL.

If the reconfiguration fails, the network part sends 406A a replymessage BEARER_FAIL informing that the reconfiguration failed. In thiscase the reply message comprises the radio bearer identifier BID and acause CAUSE for the failure of the reconfiguration.

If the radio network sublayer MS RNL requested in the reconfigurationrequest message BEARER_RECONF_REQ the reconfiguration of several radiobearers and in case all the reconfigurations succeed, the reply messageBEARER_COMPL is sent, all the above described parts being repeated inthe message for each radio bearer. Likewise, in case all thereconfigurations fail, the above described reply message BEARER_FAIL issent, the above described parts, i.e. the radio bearer identifier BIDand the cause CAUSE for the failure of its reconfiguration, beingrepeated in the message for each radio bearer. In case some of thereconfigurations succeed and others fail, separate reply messages aresent for the successful reconfigurations and for the failed ones, oronly one message combining the structures of the successfulreconfiguration reply message BEARER_COMPL and the failedreconfiguration reply message BEARER_FAIL is sent. In this case thestructure of the reply message is for instance the following: (BID,BEARER QOS[LLC, RLC], BID, CAUSE]. Let us assume that three separateradio bearers having identifiers bid1, bid2 and bid3 were to beconfigured. Let us further assume that the reconfiguration of bid1 wassuccessful whereas the reconfiguration of the others failed. In thiscase a single reply message comprises the following: bid1, bid1 qos[bid1llc, bid1 rlc], bid2, bid2 cause, bid3, bid3 cause.

Having received the reply message the protocol software of the mobilestation changes either its transmission or its reception parameters as aresult of the successful reconfiguration, or it starts to plan its nextprocedure as a result of a failed reconfiguration.

Another way to carry out radio bearer reconfiguration initiated by amobile station is one in which the mobile station signals on a callcontrol plane to the mobile switching centre that parameters of a userservice need to be reconfigured. The mobile switching centre transmitsthe service parameters to the radio network controller where they arechanged into radio bearer parameters. The actual reconfiguration is thencarried out in the same way as if the network part had initiated it,i.e. as shown in FIG. 4B.

FIG. 4B illustrates a reconfiguration procedure initiated by the networkpart. The network part radio network sublayer NP RNL sends 400B areconfiguration request message BEARER_RECONF_REQ to the peer MS RNLlocated at the mobile station. Again, the reconfiguration requestmessage BEARER_RECONF_REQ comprises one or more radio bearer identifiersBID and corresponding quality of service BEARER QOS parameters. Sincethe LLC sublayer and RLC sublayer parameters are decided in the networkpart, the network part radio network sublayer NP RNL can directlytransfer the parameters LLC, RLC in question in the reconfigurationmessage BEARER_RECONF_REQ. The mobile station radio network sublayer MSRNL initiates the reconfiguration 402B. After a successfulreconfiguration the mobile station sends 404B the reply messageBEARER_COMPL, the only parameter of which is the radio bearer identifierBID. After a failed reconfiguration the mobile station sends 406B thereply message BEARER_FAIL comprising the radio bearer identifier BID andthe cause CAUSE of the failure as parameters. As described in connectionwith FIG. 4A, a plural number of radio beares can be simultaneouslyreconfigured and, similarly, the reply message can be a combination ofreply messages to a successful and a failed reconfiguration.

In a preferred embodiment, a completed reconfiguration does not requirea separate reply message to be sent, instead, the parties observe thesuccess or failure of the reconfiguration by detecting thesynchronization of the first layer after the operation has been carriedout. Therefore the reply message normally sent after synchronization isleft out.

In a preferred embodiment the BEARER_RECONF_REQ parameters comprise atleast one of the following parameters:

-   -   radio bearer identifier BID;    -   radio bearer quality of service BEARER QOS of the bearer        concerned;    -   radio bearer cipher parameters, such as cipher mode on/off,        optionally a cipher algorithm or key;    -   RLC/MAC sublayer processing parameters, such as: RLC protocol        unit size, temporary mobile station identity or a transport        format set, the MAC sublayer selecting from the transport format        set one transport format for each physical layer frame of ten        milliseconds on the basis of the bit rate needed at a particular        moment;    -   physical layer processing parameters, such as a downlink        channelization code, optionally an uplink channelization code;        time of change indicator, i.e. the number of the frame from        which on the reconfiguration is to be carried out.

A difference in the principle of the reconfiguration methods illustratedin FIGS. 4A and 4B is that the network part has more power of decision.In a method according to FIG. 4A the network part can change the qualityof service requested by the mobile station, whereas a mobile stationaccording to FIG. 4B can only either approve or reject the quality ofservice determined by the network part. When the mobile station has toreject the reconfiguration requested by the network part, it possiblystarts to release the radio bearer or to perform handover.

Reconfiguration can be carried out both for signalling radio bearers andcommunication radio bearers.

The radio bearer quality of service BEARER QOS can be indicated invarious ways. The most typical way is to use at least one parameterindicating the quality of service. The parameter may well guide theoperation of the protocols directly, by providing the LLC and the RLCsublayers directly with operational parameters, for example. A parametercan also denote different quality aspects, such as a maximum bit errorrate, a maximum transmission delay allowed, a transmission delaydeviation, radio bearer priority, radio bearer security, data loss athandover, i.e. whether it is allowed to lose data in connection withhandover.

The invention is advantageously implemented by software, the inventionthus requiring functions in the protocol processing software located inthe control unit 124 of the base station controller 102 and into theprotocol processing software located in the transceiver processor 214 ofthe mobile station 150.

Even though the invention is described above with reference to anexample shown in the attached drawings, it is apparent that theinvention is not restricted to it, but can vary in many ways within theinventive idea disclosed in the attached claims.

1. A cellular radio network comprising: a protocol software of a networklayer of a network part arranged to establish a connection to a mobilestation through at least one radio bearer; a protocol software of anetwork layer of the mobile station arranged to establish a connectionto the network part through at least one radio bearer; the protocolsoftware of the network layer of the network part is further arranged totransmit to the protocol software of the network layer of the mobilestation a radio bearer reconfiguration request message concerning atleast one radio bearer; and the protocol software of the network layerof the mobile station is further arranged to transmit to the protocolsoftware of the network layer of the network part a reply message to theradio bearer recognition request message, wherein the radio bearerreconfiguration request message comprises at least one radio beareridentifier and bearer quality of service of the radio bearer inquestion.
 2. A cellular radio network comprising: a protocol software ofa network layer of a network part arranged to establish a connection toa mobile station through at least one radio bearer; a protocol softwareof a network layer of the mobile station arranged to establish aconnection to the network part through at least one radio bearer; theprotocol software of the network layer of the network part is furtherarranged to transmit to the protocol software of the network layer ofthe mobile station a radio bearer reconfiguration request messageconcerning at least one radio bearer; and the protocol software of thenetwork layer of the mobile station is further arranged to transmit tothe protocol software of the network layer of the network part a replymessage to the radio bearer reconfiguration request message, wherein thereply message comprises at least one radio bearer identifier and a causefor a failed reconfiguration of the radio bearer in question.
 3. Acellular radio network according to claim 1, wherein the bearer qualityof service is indicated by at least one parameter.
 4. A cellular radionetwork according to claim 3, wherein the parameter is selected from agroup consisting of bit error rate, maximum transmission delay,transmission delay deviation, priority, security and data loss athandover.
 5. A cellular radio network according to claim 3, wherein theparameter is at least one LLC sublayer parameter.
 6. A cellular radionetwork according to clam 3, wherein the parameter is at least one RLCsublayer parameter.
 7. A cellular radio network according to claim 1,wherein the radio bearer is arranged to be used for signalling.
 8. Acellular radio network according to claim 1, wherein the radio bearer isarranged to be used for communication.
 9. A cellular radio networkcomprising: a protocol software of a network layer of a network partarranged to establish a connection to a mobile station through at leastone radio bearer; a protocol software of a network layer of the mobilestation arranged to establish a connection to the network part throughat least one radio bearer; the protocol software of the network layer ofthe mobile station is further arranged to transmit to the protocolsoftware of the network layer of the network part a radio bearerreconfiguration request message concerning at least one radio bearer;the protocol software of the network layer of the network part isfurther arranged to transmit to the protocol software of the networklayer of the mobile station a reply message to the radio bearerreconfiguration request message, wherein the radio bearerreconfiguration request message comprises at least one radio beareridentifier and bearer quality of service of the radio bearer inquestion.
 10. A cellular radio network according to claim 9, wherein thereply message comprises at least one radio bearer identifier, and acause for a failed reconfiguration of the radio bearer in question. 11.A cellular radio network according to claim 9, wherein the bearerquality of service is indicated by at least one parameter.
 12. Acellular radio network according to claim 11, wherein the parameter isselected from a group consisting of bit error rate, maximum transmissiondelay, transmission delay deviation, priority, security and data loss athandover.
 13. A cellular radio network according to claim 11, whereinthe parameter is at least one LLC sublayer parameter.
 14. A cellularradio network according to claim 11, wherein the parameter is at leastone RLC sublayer parameter.
 15. As cellular radio network according toclaim 9, wherein the radio bearer is arranged to be used for signalling.16. A cellular radio network according to claim 9, wherein the radiobearer is arranged to be used for communication.
 17. A network part of acellular network, the network part comprising: protocol software of anetwork layer of the network part arranged to have a connection to amobile station of the cellular network through at least one radiobearer; the protocol software of the network layer of the network partis further arranged to transmit a radio bearer reconfiguration requestto a protocol software of a network layer of the mobile station; and theradio bearer reconfiguration request message comprises at least oneradio bearer identifier and a bearer quality of service of the radiobearer in question.
 18. A mobile station of a cellular network, themobile station comprising: protocol software of a network layer of themobile station arranged to have a connection to a network part of thecellular network through at least one radio bearer; the protocolsoftware of a network layer of the mobile station is further arranged totransmit to a protocol software of a network layer of the network part areply message to a radio bearer reconfiguration request message; and thereply message comprises at least one radio bearer identifier and a causefor a failed reconfiguration of the radio bearer in question.